Evaluation of site amplification, structural dynamic characteristics, and structural vulnerability rating of the city of Aqaba

The potential to destroy any structure during earthquakes depends on the structural design, vulnerability rating, percentage of structural elongation as compared with the natural quiet conditions, the dynamic characteristics of structure itself, as well as the dynamic characteristics of the site. Thus, factors related to the dynamic characteristics of structure and the dynamic characteristics of the site are necessary in the design of resistant structures against earthquakes. In this study, recordings of free oscillation were made directly on 18 selected structures in the urban city of Aqaba, which represent the structural culture of the city and the whole Jordan in general. Ground ambient vibration records were conducted at 18 nearby location at a few meters away from each structure. Records were conducted during the maximal cultural activities using three-component seismometer of 2 Hz free oscillation. Analytical results of records obtained on structures, has given the following equation: $ f = {18}/N $ , where f, is the fundamental mode of structure and N, is the number of stories. All structural records were conducted at the top level of each structure except at Shmesani 4 and 7. Horizontal sensors were oriented with respect to the longitudinal and transverse direction of structural horizontal projection. Damping factors for each structural longitudinal and transverse fundamental mode were calculated based on the obtained FFT spectrums of each orientation using half-width band method. Analysis of obtained records on structures in Aqaba show that most of them are of short periodic structures except a few multi-story tall buildings. Most of the results obtained on structures refer to damping factors that range between 0.05 and 0.208. Mathematical relation derived from this study above, in addition to the actual calculated damping factor, refers to non-compliance with the standards of earthquake-resistant design. Results of ground records analysis indicate to the westward and north-westward decrease of dominant frequency relative to the eastern and southeastern part of the study area, where the crystalline granite bedrock is much shallower reflecting the actual condition of surface geology. Striking that the H/V amplification was relatively higher in the scope of areas where the thicknesses of soft surface deposits in the eastern and southeastern part are much shallower relative to the western and north-western part of the study area. This can be interpreted as a result of much higher impedance contrast in the eastern and southeastern part relative to the western and northwestern parts of the study area.     

Verification of a new method for evaluation of liquefaction potential analysis

The seismic response of existing earth dams in Iran is important after an earthquake both to provide emergency supplies and to society as well as to ensure structural safety in engineering terms. Better seismic capacity of earth dam results in less structural damage and reduced impacts following an earthquake disaster. Indirect as well as direct costs following earthquakes have gained much attention from both the engineering and socioec onomic research communities in the last few decades. This study is a valuable tool used to study the response of geotechnical structures to infrequent or extreme events such as earthquakes. The Avaj earthquake (2002, Iran) was applied to a series of model tests which was conducted to study the response of soil profiles under seismic loading. The acceleration records at different locations within the soil bed and at its surface along with the settlement records at the surface were used to analyze the soil seismic response. A combination of several software packages with a generated visual user interface computer code by authors named as “Abbas Converter” were employed to evaluate the variation of shear modulus and damping ratio with shear strain amplitude to assess their effects on site response. The proposed method was applied to the Korzan earth dam of Hamedan province in Iran. Site response analysis using the measured shear wave velocity, estimated modulus reduction, and damping ratio as input parameters produced good agreement with the computed site response in this study.     

2D inversion of the magnetotelluric data from Mahallat geothermal field in Iran using finite element approach

The natural-field magnetotelluric (MT) method has proven very useful for mapping the geothermal fields as resistivity sections. The depth of investigation of the MT method is sufficiently large to penetrate deep into the upper crust. MT soundings along two transects across Mahallat geothermal field in Iran were carried out to determine the crustal structure in the region. The selected MT profiles in the region cross over the hydrothermally altered zones and different geological structures. Data were acquired along two profiles crossing the Mahallat hot springs with a total of 28 MT stations in a frequency range of 8,000 to 0.008 Hz. Spacing between stations was kept 500 m for a good resolution. We have used the code MT2DInvMATLAB for inversion using the method of finite elements for forward modeling. Apparent resistivity and phase data of transverse electric (TE), transverse magnetic (TM), and TE + TM modes along each profile were modeled. The geothermal fluid reservoir is resolved at 1,000 to 3,000 m depth and the geothermal resource is estimated to be located at 7,000 m or deeper.     

廊固凹陷奥陶系潜山不整合输导特征与油气优势运聚方向

不整合是廊固凹陷奥陶系潜山油气运移的重要输导通道和聚集部位,研究不整合分布及其输导特征对明确该区油气优势运移方向以及寻找有利勘探目标具有重要意义.以廊固凹陷奥陶系潜山顶面不整合的类型及分布规律、纵向结构特征为基础,对潜山顶面不整合的输导性和有效性进行了分析;利用钻井、测井、岩芯等资料对半风化岩石层进行了精细解剖,明确了主力输导通道分布和渗滤空间类型;在明确不同类型不整合展布规律后结合数值模拟确定了油气优势运移方向和潜在有利勘探区.研究结果表明,河西务潜山带奥陶系顶面不整合具有4种接触关系、2种运移通道,组合形成4种油气运聚类型,其中石炭系—二叠系覆盖的褶皱区最有利于油气聚集成藏.不整合半风化岩石层的渗滤通道类型南北具有差异性,南部岩溶发育,以溶蚀缝洞为主,北部以晚期构造缝为主.纵向上,垂直渗流带和水平潜流带是不整合岩溶带中的优势运移通道.平面上,不整合输导脊是油气的优势运移路径,位于其上的构造高点是油气聚集的有利区,杨税务南潜山和中岔口潜山是下一步油气勘探的潜在目标.     

场地类别分类方案研究

基于性能的抗震设计,要求工程师设计出具有预期抗震性能的结构,一个关键因素是地震作用的确定,这在很大程度上取决于局部场地条件。通过收集和分析北京、苏州和唐山城区956个钻孔资料,建立地表20 m和30 m深土层走时平均剪切波速VS20和VS30的关系式;现场钻探获取北京城区深105 m的典型钻孔原状土样,试验给出各类土体动剪切模量和阻尼比曲线;建立北京城区170个钻孔的场地反应计算模型,采用Nakamura提出的HVSR法和陈国兴等提出的弱震法估算场地基本周期TS值,结合国内外现行抗震规范的场地分类及一些学者对场地分类的研究成果,提出两种新的场地分类建议方案：基于等效剪切波速VSE和覆盖土层厚度H（地表至剪切波速VS ≥ 500 m/s的基岩深度）的双指标场地分类方案及基于VSE、H和TS的三指标场地分类方案。提出的场地分类方案对我国现行抗震规范场地分类方法的改进有参考价值。     

冀中坳陷束鹿凹陷潜山不整合特征与油气运聚模式

本文从冀中坳陷束鹿凹陷潜山顶面不整合接触类型及分布规律、结构特征及输导类型出发,精细刻画了不整合面之下半风化岩石层的垂向岩溶分带特征。在此基础上对典型剖面烃源岩热演化、油气运移进行模拟,建立了研究区潜山油气的运聚模式。结果表明,束鹿凹陷潜山顶面不整合包括4种接触类型、5种结构模式,具有3种输导类型,其中斜坡区和洼槽区西部以侧向型为主,斜坡区局部构造高点与洼中隆为侧向+圈闭型,凸起区以侧向+垂向型为主。不整合面之下半风化岩石孔缝洞体系发育,垂向上可划分为表层岩溶带、垂直渗流带以及三个水平潜流带,具有多期岩溶旋回特征。潜山顶部发育的垂直渗流带是油气沿不整合面运移的主力输导层,而内幕发育的多期水平潜流带是油气向内幕运移的潜在通道。深、浅部烃源岩热演化的差异以及与薄层砾岩是否接触导致了斜坡区与洼中隆潜山油气充注的差异,形成了斜坡区晚期薄层砾岩高效中转、不整合侧向运移、水平潜流带向内幕输导、顺向断层向上输导、反向断层圈闭成藏的油气运聚模式。     

Transverse zones controlling the structural evolution of the Zipaquira Anticline (Eastern Cordillera,Colombia): Regional implications

We report paleomagnetic, magnetic fabric and structural results from 21 sites collected in Cretaceous marine mudstones and Paleogene continental sandstones from the limbs, hinge and transverse zones of the Zipaquira Anticline (ZA). The ZA is an asymmetrical fold with one limb completely overturned by processes like gravity and salt tectonics, and marked by several axis curvatures. The ZA is controlled by at least two (2) transverse zones known as the Neusa and Zipaquira Transverse Zones (NTZ and ZTZ, respectively). Magnetic mineralogy methods were applied at different sites and the main carriers of the magnetic properties are paramagnetic components with some sites being controlled by hematite and magnetite. Magnetic fabric analysis shows rigid-body rotation for the back-limb in the ZA, while the forelimb is subjected to internal deformation. Structural and paleomagnetic data shows the influence of the NTZ and ZTZ in the evolution of the different structures like the ZA and the Zipaquira, Carupa, Rio Guandoque, Las Margaritas and Neusa faults, controlling several factors as vergence, extension, fold axis curvature and stratigraphic detatchment. Clockwise rotations unraveled a block segmentation following a discontinuos model caused by transverse zones and one site reported a counter clockwise rotation associated with a left-lateral strike slip component for transverse faults (e.g. the Neusa Fault). We propose that diverse transverse zones have been active since Paleogene times, playing an important role in the tectonic evolution of the Cundinamarca sub-basin and controlling the structural evolution of folds and faults with block segmentation and rotations.     

黏弹性地基中PCC桩扭转振动响应解析方法研究

考虑土体材料的黏性阻尼和桩-土扭转耦合振动,把桩看作一维杆,将土体视作三维轴对称黏弹性介质,对黏弹性地基中现浇混凝土大直径管桩（简称PCC桩）扭转振动频域特性进行了理论研究,采用Laplace变换和分离变量的方法求得了桩顶扭转频域响应解析解。将所得解完全退化到实心桩的解,并与经典平面应变解进行对比,验证了解析解的合理性。分析了桩长以及土体黏性阻尼系数对桩顶速度导纳和复动刚度的影响,得到了各参数对桩扭转振动特性影响的规律。分析表明：桩周土黏性阻尼系数增大可以显著提高桩顶扭转复动刚度和减小速度导纳振荡幅值,而桩芯土黏性阻尼系数的影响不明显;桩长越长,桩顶复动刚度越大,速度导纳振荡幅值越小,但当桩长增大到一定程度时,再继续增加桩长,桩顶复动刚度基本没有改变。     

Vegetation covers as indicator of seismo-tectonic environment: an integrated geophysical study in north Baromura hill, India

Spatial distributions of vegetation cover are closely related to topographical characters like slope, steepness, soil types, elevations, etc. In seismo-tectonic regions fault lines or tectonic lineaments are the most prominent surface signatures that can be reflected by vegetation distribution as tectonic displacement causes the change of topographical parameters. In the present study a part of northern Baromura hill (between 23º 42′ N to 23º49 N latitudes and 91º30 E to 91º36 E longitudes), which is considered as an active seismo-tectonic region of Tripura as well as northeast India, was selected for assessing the relationship between spatial variation of plant cover and topography. Geologically, Baromura hill is a north–south extended fold belt and formed by late Tertiary to Quaternary depositions. Evidences show that tectonic events played very important role in landform evolution of this area during the geological past. In this research an extensive fieldwork was conducted in the study area to understand the geomorphic and vegetation signatures and their environmental relationships. Various spectral resolutions of Landsat ETM+ were used for digital analysis. To analyse the vegetation character of this area digital operation was done within the spectral range 0.63–1.75 μm. Band 4 and band 3 were used for NDVI operation. Band 5 or mid-wave infrared band was classified in unsupervised mode to understand the range of plant water in the study area. Overlay operation with those operated images shows the spatial distribution pattern of vegetation cover indicates the landform condition. Three clear tectonic lineaments (faults) were detected from the digital study in on the northern part Baromura hill. Structural conditions of those fault lines were verified by geo-electrical survey during fieldwork. GPS tool was used for fixing the ground control points. Resistivity characters of the study area assessed from VES profile strongly supports that vegetation cover analysis from remotely sensed data within 0.63–1.75 μm spectral ranges can be a very useful tool for detecting surface tectonic signatures of the landform.     

Structural analysis of sheath folds and geochronology in the Cuonadong Dome,southern Tibet,China: New constraints on the timing of the South Tibetan detachment system and its relationship to North Himalayan Gneiss Domes

Structural analysis and new zircon U/Pb geochronology were performed in the Cuonadong Dome in order to test the hypothesis that the top‐to‐North deformation in the North Himalayan Gneiss Domes (NHGD) has been correlated with deformation along the South Tibetan detachment system (STDS). Structural analysis suggests that the X‐axes of sheath folds at the different flanks of the dome are consistent, and show average a trend and plunge of 350° and 18°. Many shear sense indicators are recorded in the ductile shear zone during the top‐to‐north deformation, including the augen structure, σ‐type and δ‐type rotating porphyroclast, S–C fabric and pressure shadow structure. The development of the sheath folds first provide a direct‐field structural evidence that represents a deeper ductile manifestation of the STDS, and further suggests that the top‐to‐north deformation in the NHGD have been correlated with deformation along the STDS. The emplacement of the synkinematic granites at ca. 32 Ma exposed at the core of the sheath folds is also interpreted as the initiation of slip along the STDS.     

运营期水下盾构隧道管片接缝张开度变化规律

水下盾构隧道管片间接缝张开度对隧道防水及运营期结构安全有重要影响。以南京扬子江隧道结构健康监测系统中两个典型监测断面的接缝监测数据为基础,通过多元线性回归分析方法分析在两种不同地层组合下接缝张开度随水位、温度变化的规律;并对接缝张开度随水位变化的规律进行了有限元数值模拟,数值模拟结果与回归分析结果吻合较好。上述分析结果表明,纵缝张开度和横缝张开度随水位、温度的变化均呈现较好的线性关系,具体变化趋势如下：当盾构隧道穿越上砂下岩的上透下不透地层时,环内上半部分管片纵缝张开度随水位的增大而增大,受温度影响则相对较小;当盾构隧道穿越砂性全透水地层时,环内管片纵缝张开度随水位的增大而减小,受温度影响也相对较小;环间横缝张开度在上述两种地层下随水位、温度的变化趋势相同,均随水位增大而增大,随温度的升高而减小。     

滑脱型潜山成藏研究--以沾化凹陷渤深6潜山为例

渤深6潜山于早第三纪初期与埕东凸起分离,沿边界断层滑脱至渤南洼陷,后期为第三系覆盖,是济阳坳陷中典型的滑脱型潜山.在多期构造运动及古岩溶作用下,潜山中以碳酸盐岩为主的下古生界形成良好的储集空间.渤南洼陷中沙三段烃源岩为潜山提供了充足的油源,潜山内幕发育的断层为油气的运移提供了良好的通道,从而在潜山顶部形成风化壳油藏,而在潜山内幕则形成层状油藏.该潜山油气藏具有埋藏深、破碎严重、含油层系多、单井产能高且不含水的特点.研究渤深6潜山的成藏机制对指导断陷盆地深层滑脱型潜山油气藏的勘探具有指导意义.     

Ground motion amplification due to shallow cavities in nonlinear soils

Subsurface cavities or stiff inclusions represent mechanical discontinuities for seismic waves propagating in soils. They modify the propagation pattern of seismic waves and alter soil response in correspondence to the ground level or building foundations. In the literature, different analytical and numerical solutions have been proposed to account for the effect of underground cavities or inclusions on the motion generated by P, S or R waves. In these former studies, the subsoil was assimilated to a homogeneous, isotropic and linear elastic halfspace containing one or more cavities. In the present study, the effect of subsurface cavities on ground motion amplification has been analysed accounting for soil stiffness degradation and associated damping increase with increasing levels of shear strains, a fundamental aspect of soil behaviour under earthquakes. The analysed model was inspired to a real case represented by the village of Castelnuovo (Italy), which during the 2009 Abruzzo earthquake suffered huge damage. The main shock (6 April 2009) caused the collapse of 50 % of the whole built environment. The historical centre of Castelnuovo rises on a hill. In its subsoil, there are many cavities with roofs 2–3 m below the ground level. The longitudinal NW–SE section of the hill has been investigated by 2D nonlinear site response analyses. A preliminary site response analysis was performed without modelling cavities, to identify ground motion amplification due to mere stratigraphic and topographic factors. The numerical model was later refined inserting: (1) a single cavity below the hilltop, (2) multiple cavities placed below the ground surface of the hill and (3) multiple cavities filled with concrete (inclusions). The performed study highlights the important role exerted by underground cavities on the ground motion computed at the hill surface. This effect should be properly considered for both microzonation studies and the correct determination of the seismic actions on specific buildings.     

Determination of acoustic phonon dispersion curves in layer silicates by inelastic neutron scattering and computer simulation techniques

Inelastic neutron scattering and computer modelling techniques have been used to study acoustic phonons in several layer silicate minerals. Experimental measurements have been made on four layer silicate minerals; namely samples of muscovite, Fe-bearing muscovite, margarite and chlorite. The longitudinal acoustic modes propagating along the [0, 0, ξ] direction of muscovite and Fe-bearing muscovite were found to be the same, within experimental error. The longitudinal and transverse acoustic modes propagating along [0, 0, ξ] of muscovite have been calculated using computer simulation techniques based on lattice dynamics. The experimental and calculated longitudinal modes of muscovite are in excellent agreement, thereby demonstrating the complementary nature of both techniques. The shape of both experimental and calculated dispersion curves was found to be approximately sinusoidal, indicating that interatomic forces act principally between nearest-neighbour atoms.     

塔北古隆起的三维地质结构及相关问题探讨

盆地深层构造地质学的研究可以揭示沉积盆地早期的物质记录,揭示盆地深层地质结构、构造样式及其变化特点,还原构造-古地理环境等。塔北古隆起是塔里木盆地油气最富集的构造单元之一,是研究板块内部变形的理想场所。对塔北古隆起地质结构的精细解析有利于加深对古隆起控油气理论的理解,对深层海相油气勘探具有指导意义。文中基于整个塔北地区的地震资料以及大量钻井资料,建立其三维地质结构,通过Petrel软件实现三维可视化。塔北古隆起存在12个不整合面,可划分为五大构造层:基底(AnZ)、震旦系—下古生界(Z-S)、上古生界(D3d-P)、中生界(T-K1)、新生界(E-Q)构造层。塔北古隆起的地质结构受其深层主干断裂系统控制,依据深层主干断裂发育模式的差异,可将古隆起分为4段:(Ⅰ)温宿凸起段;(Ⅱ)英买力低凸起段;(Ⅲ)哈拉哈塘凹陷与轮南低凸起段;(Ⅳ)草湖凹陷与库尔勒鼻状凸起段。哈拉哈塘凹陷-库尔勒鼻状凸起(甚至包括孔雀河斜坡)的古生界构造层保留了NE-SW向的古生代构造形迹,与近E-W向深层主干断裂系统斜交,可能指示塔北古隆起在晚古生代处于右旋压扭性或NW-SE向主应力环境,直到侏罗纪—早白垩世才发生改变。     

龙游石窟结构的力学思想

龙游大型地下石窟群埋藏浅、跨度大,且位于软岩中。千年以来保持稳定的重要原因,除了岩体的完整性较好和洞体内所充满的水对洞顶的支撑作用以外,就是采用了比较特殊的结构形式。石窟在纵向分别利用了斜顶结构,在横向采用了拱状结构,加大柱纵向支撑长度的鱼尾形柱结构和扩大柱端头的柱帽结构。将这些结构形式与现代结构力学原理相比较发现,它们完全符合现代结构力学的原理,是科学的。它们体现了古人的结构力学思想,折射出了我国古人的智慧和创造力。通过发掘和研究石窟蕴涵的结构力学思想,可以做到古为今用,指导目前越来越多的地下工程建设。     

成层饱和土中考虑横向惯性的单桩纵向振动

基于饱和多孔介质理论,研究了成层饱和黏弹性土层中端承桩的纵向振动特性。首先利用Novak薄层法,得到了土层对纵向振动桩的动力阻抗。其次,将桩等效为Rayleigh-Love杆,给出了成层饱和黏弹性土中端承桩纵向振动的一般分析方法和桩头动力复刚度的解析表达式。具体分析了两层饱和黏弹性土中端承桩的纵向振动特性,得到了桩头动刚度因子和等效阻尼随频率的响应特征,讨论了物理和几何等参数对动刚度因子和等效阻尼的影响。结果表明：桩长径比、土层模量比以及桩土模量比等对桩头动刚度因子和等效阻尼有显著的影响。相比于均质土层中的桩,上层土越硬或下层为软弱土层,桩的动刚度因子和等效阻尼振动幅值增大,其周期随长径比显著变化,且对于大直径桩,动刚度因子和等效阻尼随频率呈振动变化。同时,土体与孔隙水相互作用系数和桩泊松比等的影响相对较小。其结果可作为桩基动力基础设计和动力检测等基础数据。     

Site effects close to structural lineaments in eastern Sicily (Italy)

This paper analyses site effects that are applied to compute the H/V spectral ratio close to structural lineaments. Aseismic creep and seismic creep have been examined. The lineaments are located in different types of volcanic soil. The aim of the work is to verify the possibility of fault-guided seismic waves within the structures, which behave as a waveguide for trapped waves.

The measurements of ambient noise were carried out along profiles crossing the structures, and the standard Nakamura technique was applied to calculate the spectral H/V ratio. It was observed that horizontal components of ground motion were found to be significantly amplified within the shear zone.     

钻柱振动特性的仿真分析

钻进过程中,钻柱振动是不可避免的,而且钻柱产生振动的原因是多方面的。随着研究的深入,人们不仅认识到钻柱振动对钻井作业产生的负面影响,还认识到利用振动可以得到许多井下信息。运用一根钻杆模型,分析了其在不同工作状况下的振动特性,得到了钻杆在横向、纵向、扭转振动的多阶振型,以及对应的应力应变图。对照振型和应力应变图,联系钻井实践中各种钻柱失效形式,以期从中找出一些振动与钻柱失效的关联,更好地利用振动去解决生产问题。     

Insight into sequence stratigraphic and structural framework of the onshore Niger Delta Basin: Integrating well logs,biostratigraphy, and 3D seismic data

Stratigraphic and structural interpretative studies have been carried out within the paralic sequence of Agbada Formation in the Niger Delta Basin. The method of study involved integrating sequence stratigraphic techniques with well logs, biostratigraphy, and 3D regional seismic data obtained from several producing fields in the Coastal Swamp depobelt of the onshore Niger Delta Basin. This was targeted at establishing regional sequence stratigraphic and structural framework from well log correlation and seismic mapping so as to better define hydrocarbon leads. Well log correlation using stratigraphic bounding surfaces such as maximum flooding surfaces (MFSs) and sequence boundaries (SBs) indicates that the stratigraphic package was deposited within the Middle to Late Miocene (8.5 to 12.1 Ma) age. Recognized depositional sequences revealed differential thickening and thinning of the associated system tracts (lowstand system tract (LST), transgressive system tract (TST), and highstand system tract) (HST)). This observed stratal behavior has been attributed to the influence of syndepositional tectonic structures that characterize the Coastal Swamp depobelt, which lies within the extensional zone. Flattening of MFSs at various ages indicates observable basinward shift of the depositional center. The genetic units of LST and HST serve as good hydrocarbon reservoir whereas HST and TST constitutes mainly the source and seal packages rocks in the area. Structural interpretation revealed the occurrence of simple/faulted rollover anticline, collapsed crest, regional hanging wall and footwall, horst block, and subdetachment fault structural styles that constitute the key hydrocarbon entrapment mechanisms. Structural top maps show fault-dependent closures which dominate the extensional zone, which could form possible hydrocarbon leads and prospects that should be targeted during exploration studies for development.